Folks,
I am installing the current limiters in my plane. The engine is a Lycoming IO-360 with a primary alternator (the belt driven one that came with the used engine) and a B&C Aero backup alternator. Here is the photo:
[img]cid:ii_jguvydjb0_16335c1f8da88efe[/img]
I tied the ends together with a piece of brass buss bar from B&C. Spec says that it is .025 x .5. Is that sufficient to carry the load for this plane? My analysis has these loads:
Typical 19 amps, 29 amps maximum
With all devices on, including pitot heat: typical 32 amps, 49 amps maximum
Also, B&C Aero shipped the current limiter holders with locknuts that have plastic inserts. Are those OK on the engine side of the firewall? I thought that I should only use all-metal locknuts on the engine side.
-- Art Z.

Also, B&C Aero shipped the current limiter holders with locknuts that have plastic inserts. Are those OK on the engine side of the firewall? I thought that I should only use all-metal locknuts on the engine side.

art(at)zemon.name wrote:
> Also, B&C Aero shipped the current limiter holders with locknuts that have plastic inserts. Are those OK on the engine side of the firewall? I thought that I should only use all-metal locknuts on the engine side.

The elastic nuts are fine off the engine.

Bob . . .

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Bob,
Do you have any opinion on whether the "bus bar" has sufficient current carrying capacity? I have a gut feeling that it is OK, since there is plenty of airflow around it but I lack the engineering/practical knowledge to make an objective determination.
To save you looking for the original message, I used the brass bus bar supplied by B&C Aero as part of a backup alternator installation kit. The material is 0.025 x 0.5 x 2 inches. It needs to carry 19 amps typical load (32 amps with everything on). The maximum (all radios transmitting, both autopilot servos drawing full current, etc) is 49 amps.
​ -- Art Z.​
--
https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

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The area of your bus bar is 0.025 x 0.5 = 0.0125
0.0125 equals 12,500 circular mills which is slightly bigger than 10 AWG.
Your bus bar should be good for 30 to 40 amps depending on what wire table you look at. If my calculations and reasoning is correct, your bus bar should be OK.
You can make your own bus bar out of flattened copper pipe or tube. I would clean the inside of the tube, then flatten and then solder the inside to keep out contaminants and prevent corrosion.

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Do you have any opinion on whether the "bus bar" has sufficient current carrying capacity? I have a gut feeling that it is OK, since there is plenty of airflow around it but I lack the engineering/practical knowledge to make an objective determination.

To save you looking for the original message, I used the brass bus bar supplied by B&C Aero as part of a backup alternator installation kit. The material is 0.025 x 0.5 x 2 inches. It needs to carry 19 amps typical load (32 amps with everything on). The maximum (all radios transmitting, both autopilot servos drawing full current, etc) is 49 amps.

​ -- Art Z.​

Art,

1st, determine what gauge wire you'd need for 50 amps. Easy to find it in the book, or the internet, But to save time, it's 8 awg. You can use the internet to find its cross sectional area (~0.0130 sq in). Then calculate the cross section if your strap (~0.0125 sq in). Probably would be fine, but it would be really easy to just add another layer of the brass strap. Or cheap out like me & flatten a section of copper tubing to make the strap.

Joe,
Thank you for that calculation. It sounds like thicker material would be better. I think that I will try flattening a piece of copper tube. Any excuse to play with a hydraulic press and solder in the same day is a good excuse 😜
-- Art Z.

The area of your bus bar is 0.025 x 0.5 = 0.0125
0.0125 equals 12,500 circular mills which is slightly bigger than 10 AWG.
Your bus bar should be good for 30 to 40 amps depending on what wire table you look at. If my calculations and reasoning is correct, your bus bar should be OK.
You can make your own bus bar out of flattened copper pipe or tube. I would clean the inside of the tube, then flatten and then solder the inside to keep out contaminants and prevent corrosion.

Art:
When you ask a question about 'are Elastic Stop Nuts being OK', you step out of the realm of experimental into certified.
NO! Elastic Stop Nuts are not acceptable anywhere under the engine cowl. <--- That is per a Certified Plane. Which side of the fence do you want sit on?
Not even with star-washers under them.
Now! Is the Manufacture of the current limiter correct in supplying Elastic Stop Nuts? Maybe? Maybe they are just being nice supplying them. After all, they Do Not Know where you are installing them!

The other question that comes up is the location of the 'current limiters' - Putting them in an air flow INCREASES the current limiting point of the limiter. What does the specs say about the safety range of them? What was the ambient temperature of the testing?
Barry

Folks,
I am installing the current limiters in my plane. The engine is a Lycoming IO-360 with a primary alternator (the belt driven one that came with the used engine) and a B&C Aero backup alternator. Here is the photo:
[img]cid:ii_jguvydjb0_16335c1f8da88efe[/img]
I tied the ends together with a piece of brass buss bar from B&C. Spec says that it is .025 x .5. Is that sufficient to carry the load for this plane? My analysis has these loads:
Typical 19 amps, 29 amps maximum
With all devices on, including pitot heat: typical 32 amps, 49 amps maximum
Also, B&C Aero shipped the current limiter holders with locknuts that have plastic inserts. Are those OK on the engine side of the firewall? I thought that I should only use all-metal locknuts on the engine side.
-- Art Z.

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